This invention relates to a process for manufacturing a magnetic record member, such as a magnetic disk or a magnetic drum, and to a magnetic record member which is of the structure suitably manufactured by the process.
It is usual that a magnetic record member comprises a substrate of at least one non-magnetic material and a thin film of a magnetic metal thereon. Such a magnetic record member is used in a magnetic recording device, which is used in, among others, a data processing system. The magnetic recording device comprises a magnetic head, as called herein, relative to which the magnetic record member is movable. Responsive to electrical signals, the head records the electrical signals as magnetization in the magnetic metal film along a track. The magnetic metal film keeps the magnetization as records of the electrical signals. The head is used also in reproducing the electrical signals from the records and in erasing the records. Such function of a magnetic recording device will be referred to herein as "operation" of the device. When a plurality of magnetic heads are used, the operation is carried out along a plurality of tracks, respectively, which are concentric in a magnetic disk and either parallel or helical in a magnetic drum.
For a magnetic record device in which the magnetic record member is moved relative to the head or heads at a high speed, it is preferred to resort to the contact-start-stop method (hereafter abbreviated to CSS method), as called in the art. According to the CSS method, the head is in contact with the magnetic record member at rest before start of operation of the device. During operation, a layer of air is formed as a result of the relative movement between the head and the magnetic record member. On carrying out stop of the operation, the head is brought into contact with the magnetic record member so as to rest in contact therewith. During the high speed relative movement, the air layer serves to avoid friction between the head and the magnetic record member.
Even with the CSS method, it is inevitable that the head is in frictional contact with the magnetic record member at the start and stop and also in some unexpected cases. The friction results in mechanical wear of the head and the magnetic record member and goes worse, as the case may be, to damage either or both. The magnetic metal film is subject to chemical attack by a humid atmosphere and the like if left exposed to the environment. It is therefore important to form a protective layer on the magnetic metal film for protecting the latter against the mechanical wear and/or damage and the chemical attack. It is preferable that the protective layer could further serve to protect the head. In addition, the magnetic record member is subject to scratch by a tip or an edge of something hard. It is therefore desirable that the protective layer should protect the magnetic metal film against such scratches.
A magnetic record member comprising a polysilicate film or layer on the magnetic metal film is disclosed in U.S. Pat. No. 4,162,350 issued to Masahiro Yanagisawa, the present applicant, et al and assigned to the present assignee. The polysilicate layer is formed by applying a solution of tetrahydroxysilane onto the magnetic metal film to form a layer of the solution and then baking the layer of solution at a raised temperature during a predetermined interval of time. It is mandatory that the recording and the reproducing characteristics of the magnetic metal film should not be adversely affected during the baking step as a result of deterioration in magnetic properties of the magnetic metal film and undesired magnetization of the substrate. The polysilicate layer serves as an excellent protective layer as discussed in detail in the cited United States patent. It would be more advantageous if the reliability of such a polysilicate layer could further be raised.